Refactor markup render system (#32612)

This PR removes (almost) all path tricks, and introduces "renderhelper"
package.

Now we can clearly see the rendering behaviors for comment/file/wiki,
more details are in "renderhelper" tests.

Fix #31411 , fix #18592, fix #25632 and maybe more problems. (ps: fix
#32608 by the way)

modules/markup/html_node.go

@@ -4,8 +4,6 @@
 package markup
 
 import (
-	"code.gitea.io/gitea/modules/util"
-
 	"golang.org/x/net/html"
 )
 
@@ -17,7 +15,7 @@ func visitNodeImg(ctx *RenderContext, img *html.Node) (next *html.Node) {
 		}
 
 		if IsNonEmptyRelativePath(attr.Val) {
-			attr.Val = util.URLJoin(ctx.RenderOptions.Links.ResolveMediaLink(ctx.IsMarkupContentWiki()), attr.Val)
+			attr.Val = ctx.RenderHelper.ResolveLink(attr.Val, LinkTypeMedia)
 
 			// By default, the "<img>" tag should also be clickable,
 			// because frontend use `<img>` to paste the re-scaled image into the markdown,
@@ -53,7 +51,7 @@ func visitNodeVideo(ctx *RenderContext, node *html.Node) (next *html.Node) {
 			continue
 		}
 		if IsNonEmptyRelativePath(attr.Val) {
-			attr.Val = util.URLJoin(ctx.RenderOptions.Links.ResolveMediaLink(ctx.IsMarkupContentWiki()), attr.Val)
+			attr.Val = ctx.RenderHelper.ResolveLink(attr.Val, LinkTypeMedia)
 		}
 		attr.Val = camoHandleLink(attr.Val)
 		node.Attr[i] = attr